Methods of this kind are used together with bar code readers, with the bar code reader transmitting a scanning beam in the direction of the bar code to be detected. The scanning beam is, for example, deflected via a rotating, polygonal mirror wheel, so that the scanning beam is periodically swept through a scanning angle. Through the moving scanning beam a scanning line is projected onto the object carrying the bar code, i.e. onto the bar code.
Most known methods require, for the successful decoding of a bar code, that the scanning beam sweeps over the bar code over its entire length. This condition is, however, no longer satisfied when the bar code to be detected is so tilted relative to the scanning direction that the scanning line projected onto the bar code no longer covers the bar code over its full length. This can, for example, be the case when the bar code is located on an article of luggage which is transported on a conveyor belt. The bar code can in this respect adopt any desired position, so that it is not ensured that a scanning beam sweeping over the object sweeps over the bar code over its full length.
In order to increase the probability of decoding it is thus published German patent application DE-A-107 118 73 that a bar code which is moving obliquely to the scanning direction should be multiply scanned by the same scanning beam, so that different adjacent regions of the bar code are obliquely swept over by the scanning beam as a result of the relative movement between the bar code and the scanning line.
The code segments of the bar code which are respectively detected during this, are combined in an image memory into a complete bar code, with the association of the code element sections respectively forming the same code element of the bar code and detected by the oblique scanning taking place by determining the angle of tilting, the so-called tilt angle, between the scanning direction and the longitudinal direction of the bar code. Once the bar code has been fully built up in the image memory, it is decoded with conventional methods.
All these methods have the common feature that for a successful detection and decoding of the bar code the latter is swept over by a scanning beam of a single bar code reader either in one passage, or, with oblique scanning, in a plurality of directly sequential passages along parallel scanning lines.
A problem exists in that bar codes which are not completely readable from the direction of the bar code reader cannot be fully detected and are thus not decodable with this method, for example due to a partial obscuring of the bar code, because of a bent or kinked bar code, because of an unfavorable reading angle, or because of a partly destroyed bar code.